Definite Integral Properties

To know the Definite Integral Properties, we should first understand what integrals are. In mathematics, the integral is a concept used to calculate the value of quantities such as displacement, area, and many others. Let us learn about definite integral properties with the help of these study material notes on definite integral properties.

An integral is a mathematical notion that explains displacement, area, volume, and other ideas that combine infinitesimal data. Integration, like differentiation, is a fundamental, essential operation of calculus that can be used to answer problems in math and physics involving the area of an arbitrary form, the length of a curve, or the volume of a solid.

Integration was first studied in the third century BC when it was used to calculate the area of circles and parabolas.

Types of Integration:

There are two types of integration, namely, definite Integrals and indefinite integrals:

· Definite Integrals:

A definite integral is an integral of a function having integration limits. The interval of integration has two values: the lower limit, which is one and the top limit. There is no consistent integration in it.

·Indefinite Integrals:

When there is no limit for integration, it is an integral function. 

We will now have a look at the definite integral properties study material in detail.

Definition of Definite Integral:

In a graph, the area of a curve can be calculated using the Definite Integral. It has start and endpoints within which the area under a curve is determined, and it has limits. To determine the area of the curve f(x) concerning the x-axis, use the limit points [a, b]. The corresponding definite integral expression is abf(x)dx. The total of the areas is integration, and definite integrals are used to calculate the area within limitations.

A definite integral is an area below a curve between two set limits. 

For a function f(x) defined concerning the x-axis, the definite integral would be written as:

 abf(x)dx, where “a” is the lower limit, and “b” is the upper limit. We split the area under a curve between two limits into rectangles and added them to find the area under the curve. The more rectangles there are, the more precise the region is.

 As a result, we divide the area into an unlimited number of rectangles, each of which is the same small size, and then add all the areas together.

The formula of Definite Integral:

There are two formulas to evaluate integrals; they are as mentioned below –

1. Definite Integral as a Limit Sum:

We divide the area under the curve into numerous rectangles by dividing [a, b] into an unlimited number of subintervals using this approach to assess a definite integral ∫ab(x)dx.

Therefore, the formula would be- 

ab∫f(x)dx =nh=1n hf(a+rh)

 Here, h is the length of the subinterval.

2. Fundamental Theorem of Calculus:

This is the most straightforward method of calculating a definite integral. This formula states that you must first determine the antiderivative (indefinite integral) of f(x) (and represent it as F(x)), then substitute the upper and lower limits one by one, then subtract the results in order. i.e.,

abf(x)dx= F(b) – F(a)

Where, F’ (x) = f (x)

Definite Integral Properties:

The definite integral properties help estimate the integral for a function multiplied by a constant, the sum of functions, and even and odd functions. Let’s look at some properties of definite integrals that can help us solve problems with definite integrals.

1.ab  f(x) dx = ab  f(t) dt

2. abf(x) dx = – abf(x) dx … [Also, aa f(x) dx = 0]
3. abf(x) dx =acf(x) dx +cbf(x) dx
4. aaf(x)dx = 0

5.ab  cf(x)dx = cab f(x)dx

6. abf(x) ± g (x) dx= abf(x) dx ± abg(x)dx 

1st Property:

ab  f(x) dx =ab  f(t) dt – This property points out that as long as the function and limits remain the same, the integration variable we employ in the definite integral does not affect the result.

2nd Property:

ab  f(x) dx = – ab  f(x) dx – Any definite integral’s limits can be exchanged; all we have to do is add a minus sign to the integral.

3rd Property:

ab  f(x) dx = ac f(x) dx + cb f(x) dx – Here, C= any number. This property is much more significant than we may think at first. This characteristic is useful for telling us how to integrate a function over the adjacent intervals [a,c] and [c,b]. However, it should be noted that c does not have to be between a and b.

4th Property:

aa f(x)dx = 0 – There is no work to be done if both the upper and lower limits are the same; the integral is 0.

5th Property:

ab cf(x)dx = cab f(x)dx – Here, c can be any number. We can factor out a constant just like we can with limits, derivatives, and indefinite integrals.

6th Property:

ab f(x) ± g (x) dx= ab f(x) dx ±ab g(x)dx – Definite integrals can be broken out across a sum or difference.

Conclusion:

Definite integrals are an essential aspect in the field of mathematics. The area under, above, and between curves can be calculated using definite integrals. The area between a function and the x-axis is the definite integral if the function is strictly positive. The area is -1 times the definite integral if it is just negative.